This invention relates to air by-pass valves and, more particularly, to an improvement in a by-pass valve in which controlled air dumps are made during decelerations to prevent engine backfires.
By-pass valves are typically used in the exhaust system of an internal combustion engine to supply air to the catalytic converter installed in the exhaust system, thus to obtain more complete combustion of fuel and reduced exhaust emissions. One problem encountered with the use of by-pass valves is engine backfires which may occur when the engine is decelerated. Engine backfires may be prevented, if, during an engine deceleration, the supply of air to the converter is shut off. However, it is important that the time interval during which air is shut off be properly controlled. If the shut off interval is too short, engine backfire may still occur. If the interval is too long, unburned fuel will be exhausted through the converter, thus increasing engine emissions.
In addition, it may also be desirable to shut off air flow to the converter during portions of the engine's operating cycle. Thus, when the engine is cold, it may be advantageous to shut off air flow only during engine decelerations, while, after the engine has warmed up and entered the "cruise" portion of its operating cycle, it may be advantageous to shut off air flow to the converter all the time and not just during decelerations.